Wireless telephone service is typically provided by a plurality of mobile telephone service providers. Each mobile telephone service provider provides "local" wireless telephone service to its subscribers. Each wireless telephone service provider may also provide so-called "roaming" wireless telephone service to the subscribers of other wireless telephone service providers. In order to place a telephone call to the wireless telephone station of a person who is roaming outside of his local area and is being served by a wireless telephone service provider other than his local wireless telephone service provider, i.e., a roaming wireless telephone service provider, it is necessary to call the so-called "roamer access port" of the roaming wireless telephone service provider and to provide the mobile identification number (MIN), i.e., the telephone number, of the called person.